length YAMAHA WR 450F 2016 Owner's Manual

CHAIN DRIVE
5-69
EAS23420REMOVING THE DRIVE CHAIN
1. Stand the vehicle on a level surface.
EWA
WARNING
Securely support the vehicle so that there is
no danger of it falling over.
TIP
Place the vehicle on a suitable stand so that the
rear wheel is elevated.
2. Remove:•Drive chain
TIP
Cut the drive chain with the drive chain cut &
rivet tool. (Use goods on the market)
EAS23441CHECKING THE DRIVE CHAIN
1. Measure:• 15-link section of the drive chain
Out of specification  Replace the drive
chain.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the length “a” between the inner sides of the pins and the length “b” between
the outer sides of the pins on a 15-link sec-
tion of the drive chain as shown in the illus-
tration.
b. Calculate the length “c” of the 15-link section of the drive chain using the following formu-
la.
Drive chain 15-link section length “c” =
(length “a” between pin inner sides + length
“b” between pin outer sides)/2
TIP
• When measuring a 15-link section of the drive chain, make sure that the drive chain is taut.
• Perform this procedure 2–3 times, at a differ-
ent location each time.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
2. Check: •Drive chain
Stiffness  Clean, lubricate, or replace.
3. Clean: •Drive chain
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Wipe the drive chain with a clean cloth.
b. Put the drive chain in kerosene and remove any remaining dirt.
c. Remove the drive chain from the kerosene and completely dry it.
ECA
NOTICE
• This vehicle has a drive chain with small
rubber O-rings “1” between the drive
chain side plates. Never use high-pressure
water or air, steam, gasoline, certain sol-
vents (e.g., benzine), or a coarse brush to
clean the drive chain. High-pressure meth-
ods could force dirt or water into the drive
chain’s internals, and solvents will deteri-
orate the O-rings. A coarse brush can also
damage the O-rings. Therefore, use only
kerosene to clean the drive chain.
• Do not soak the drive chain in kerosene for more than ten minutes, otherwise the O-
rings can be damaged.
15-link length limit
239.3 mm (9.42 in)

VALVES AND VALVE SPRINGS
6-28
g. Apply Mechanic’s blueing dye (Dykem) “b” onto the valve face.
h. Install the valve into the cylinder head.
i. Press the valve through the valve guide and onto the valve seat to make a clear impres-
sion.
j. Measure the valve seat contact width “c” again. If the valve seat contact width is out of
specification, reface and lap the valve seat.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
EAS2GC1253CHECKING THE VALVE SPRINGS
1. Measure:
• Valve spring free length “a”Out of specification  Replace the valve
spring. 2. Measure:
• Compressed valve spring force “a”
Out of specification  Replace the valve
spring.
3. Measure: • Valve spring tilt “a”Out of specification  Replace the valve
spring.
Free length (intake)
40.76 mm (1.60 in)
Limit 38.72 mm (1.52 in)
Free length (exhaust) 36.94 mm (1.45 in)
Limit 35.09 mm (1.38 in)
b. Installed length
Installed compression spring
force (intake) 178.00–204.00 N (18.15–20.80
kgf, 40.01–45.86 lbf)
Installed compression spring
force (exhaust) 124.00–142.00 N (12.64–14.48
kgf, 27.88–31.92 lbf)
Installed length (intake) 34.78 mm (1.37 in)
Installed length (exhaust) 30.83 mm (1.21 in)
Spring tilt (intake) 2.5 °/1.8 mm (2.5 °/0.07 in)
Spring tilt (exhaust) 2.5 °/1.6 mm (2.5 °/0.06 in)

ELECTRIC STARTER
6-38
EAS2GC1263CHECKING THE STARTER MOTOR
1. Check:•CommutatorDirt  Clean with 600 grit sandpaper.
2. Measure: • Commutator diameter “a”Out of specification  Replace the starter
motor.
3. Measure: • Mica undercut “a”Out of specification  Scrape the mica to
the proper measurement with a hacksaw
blade that has been grounded to fit the com-
mutator.
TIP
The mica of the commutator must be undercut
to ensure proper operation of the commutator.
4. Measure: • Armature assembly resistances (commuta-
tor and insulation)
Out of specification  Replace the starter
motor.
▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼▼
a. Measure the armature assembly resistanc-
es with the pocket tester.
b. If any resistance is out of specification, re- place the starter motor.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲
5. Measure:• Brush length “a”Out of specification  Replace the brush
set.
6. Measure: • Brush spring force
Out of specification  Replace the brush
set.
Limit
16.6 mm (0.65 in)
Mica undercut (depth) 1.50 mm (0.06 in)
Pocket tester90890-03112
Analog pocket tester YU-03112-C
Armature coil Commutator resistance “1” 0.0117–0.0143 
Insulation resistance “2” Above 1 M 
Limit 3.50 mm (0.14 in)
Brush spring force 3.92–5.88 N (400–600 gf, 14.11–
21.17 oz)

CLUTCH
6-44
EAS2GC1266REMOVING THE CLUTCH
1. Remove:• Clutch boss nut “1”
• Conical washer “2”
• Clutch boss “3”
TIP
While holding the clutch boss with the clutch
holder “4”, loosen the clutch boss nut.
EAS2GC1267CHECKING THE FRICTION PLATES
1. Check:• Friction plate
Damage/wear  Replace the friction plates
as a set.
2. Measure:
• Friction plate thicknessOut of specification  Replace the friction
plates as a set.
TIP
Measure it at four points on the friction plate.
EAS2GC1268
CHECKING THE CLUTCH PLATES
1. Check: • Clutch plate
Damage  Replace the clutch plates as a
set.
2. Measure:
• Clutch plate warpage(with a surface plate and thickness gauge
“1”)
Out of specification  Replace the clutch
plates as a set.
EAS2GC1269CHECKING THE CLUTCH SPRINGS
1. Check: • Clutch springDamage  Replace the clutch springs as a
set.
2. Measure: • Clutch spring free lengthOut of specification  Replace the clutch
springs as a set.
Universal clutch holder
90890-04086
Universal clutch holder YM-91042
Friction plate thickness 2.92–3.08 mm (0.115–0.121 in)
Wear limit 2.85 mm (0.112 in)
3 4
12
Warpage limit
0.10 mm (0.004 in)
Clutch spring free length 50.00 mm (1.97 in)
Limit 47.50 mm (1.87 in)